In the field of toners for electrophotography, with the recent tendency toward a higher image quality and a higher copying speed, it has been demanded to develop toners which have a small particle size and are excellent in low-temperature fusing ability and anti-hot offset property.
As a method for producing the toners, there are conventionally known a melt-kneading and pulverization method and a wet process such as an emulsification and aggregation method. Among them, toners obtained by the wet process (so-called chemical toners) have been noticed from the viewpoint of reducing a particle size of the toners.
As a method for enhancing a fusing performance of the chemical toners, there is disclosed a technique of adding a crosslinking agent during a process for production of the toners. For example, Patent Document 1 discloses a method for producing a chemical toner in which a carbodiimide group-containing compound as a crosslinking agent is added to emulsified particles to aggregate the emulsified particles. Patent Document 2 discloses a method for producing a chemical toner in which a compound containing two or more oxazoline groups on the average in a molecule thereof as a crosslinking agent is added to emulsified particles to subject the emulsified particles to aggregation and crosslinking reaction. Patent Document 3 discloses a method for producing a chemical toner in which an oxazoline group-containing polymer as a crosslinking agent is added to emulsified particles to aggregate the emulsified particles and thereby prepare a toner, and then the resulting toner undergoes a crosslinking reaction in a fusing step for forming images. Patent Documents 4 and 5 disclose techniques in which resin particles containing a resin binder obtained by crosslinking a resin with an oxazoline group-containing compound are directly used as a toner.    Patent Document 1: JP 2006-317715A    Patent Document 2: JP 2006-106291A    Patent Document 3: JP 2004-163854A    Patent Document 4: JP 2000-347455A    Patent Document 5: JP 10-10774A